I'd like to play some kind of debuffing fighter

[King of Nowhere]

for a short campaign - one story, a few sessions - we have to create a level 14 pc with 300k starting gold, each with a few (yet-vaguely defined) unique powers.

I picked up a dwarf with some kind of runic power to apply to equipment, because I got a concept: a grumpy old dwarf complaining about the youngsters and their fancy stuff, who proceeds to dispell/disrupt stuff.
yeah, my characters start with a silly idea that get developed seriously.

Anyway, I would like to make a martial build to dispel buffs and equipmen from people. possibly apply some other debuffs, though not tripping - I've already played that concept to the full. Possibly while quipping on the lines of "in my time we didn't have no greater heroism and we liked it"
I will have a unique power to help me, but it's not clearly defined yet, and I won't count on it.
I considered using called shots to apply debuffs, I asked the dm if he was ok with the extra bookkeeping and he hasn't replied yet, so that's a maybe.

I really don't know anything I could do for the concept, though, besides getting a dispelling weapon. I'm lookingg for ideas

[Inevitability]

Fear is the traditional way to play a debuffing fighter: get the zhentarim soldier substitution levels, burn a feat on Imperious Command, go to town.

That doesn't quite sound like what you're going for, though. Debuffs are kind of hard to get on a fighter, but you could use the sneak attack variant and then take feats that apply various status conditions (shaken, staggered, etc) on a sneak attack.

Witch Slayer gives you a 1/day swift action Disjunction effect at level 5, which is one of the closest things to what you want with a 'pure' fighter chassis, but the save is unlikely to be very high (Will vs DC 20 + your mediocre charisma is within reach of most mages) and it doesn't grant a ton of generally useful stuff in the levels leading up to it (unless possessed enemies feature heavily in the campaign).

[pabelfly]

This handbook I was reading yesterday had some good ideas for adding some abilities to mundane martials, including debuffing options:

https://minmaxforum.com/index.php?topic=11381

[Telonius]

"Fighter that debuffs" - first thing that comes to my mind is Hexblade. Or what Hexblade was trying to be, anyway.

Maybe something like a Tome of Battle class that focuses on Stone Dragon? I know it's not one of the stronger disciplines, but a bunch of the strikes limit the target's ability to act on their turn.

For disrupting things, the Mage Slayer feat line sounds like it could be what you're looking for.

[Kurald Galain]

Anyway, I would like to make a martial build to dispel buffs and equipmen from people. possibly apply some other debuffs, though not tripping
If it's a short campaign, getting all the loot may be not as important... so Sunder-specced fighter.

Alternatively, if Pathfinder material is allowed, go with Dirty Trick (https://www.d20pfsrd.com/gamemastering/Combat/#TOC-Dirty-Trick) feats (meaning sickening and/or blinding people with unsportsmanlike moves) and/or Shatterspell (https://www.d20pfsrd.com/feats/racial-feats/shatterspell-combat-dwarf/) (dispelling things by hitting them really hard).

[Anthrowhale]

You might exploit Master Thrower 5 Weak Spot + Boomerang Daze with something like Power Throw, the more esoteric Windup feat, or sneak attack+Craven to push the save out of reach and daze lock one opponent/attack/round. Rogue[Lightbringer ACF] 3/Fighter 6/Master Thrower 5 could work well.

[Biggus]

I really don't know anything I could do for the concept, though, besides getting a dispelling weapon. I'm lookingg for ideas

There are several decent debuffing weapon abilities in the MIC:

Weakening - Str penalty on crit, no save
Stunning Surge - save or be stunned 1 round (DC scales with level, Cha based), swift action to activate
Slow Burst - DC 14 will or be slowed on crit, works on creatures immune to crits, flat cost (5000GP)
Prismatic Burst - DC 20 prismatic spray on crit, works on creatures immune to crits, flat cost (30,000GP)
Paralytic Burst - DC 17 will or be paralysed 1 round on crit, works on creatures immune to crits
Enervating - 1 negative level on crit, no save
Cursespewing - multiple debuffs on crit, no save

Most are crit-based as you can see, so you'd want a weapon which crits on 15-20 (or two).

[noce]

Mage Slayer has already been mentioned, in addition to that Pierce Magic Protection automatically dispels some effects on your target. While you're at it, also grab Pierce Magical Concealment.

Another good option is Ranger dip with Favored Enemy(Arcanists): it does not dispel anything but is thematic and you can follow up with Nemesis, another thematic feat.

Regarding PrCs, Occult Slayer fits. It lets you deal more damage to casters, helps you protect from spells and gives you a Spell Turning effect.

Another PrC that dispels, couterspells and prevents casting is the Witchborn Binder in Magic of Incarnun, but is not that good.

[PoeticallyPsyco]

Fear is the traditional way to play a debuffing fighter: get the zhentarim soldier substitution levels, burn a feat on Imperious Command, go to town.

That doesn't quite sound like what you're going for, though. Debuffs are kind of hard to get on a fighter, but you could use the sneak attack variant and then take feats that apply various status conditions (shaken, staggered, etc) on a sneak attack.

Witch Slayer gives you a 1/day swift action Disjunction effect at level 5, which is one of the closest things to what you want with a 'pure' fighter chassis, but the save is unlikely to be very high (Will vs DC 20 + your mediocre charisma is within reach of most mages) and it doesn't grant a ton of generally useful stuff in the levels leading up to it (unless possessed enemies feature heavily in the campaign).

Yeah, fear and Sneak Attack are the main things you can do with a fighter. I actually had a comp build that used both, along with Iaijutsu Focus; Staggering Strike plus SA plus Iajutsu Focus plus fear penalties equals opponents having a bad time. As a PC, you'd want to cut the Ghost Template and the Supernatural Transformation feats, replacing them with, well, literally anything else. This also means you can move Human Paragon 1 to your first level if you want, making for a slightly cleaner skill progression, or even replace Human Paragon entirely with a feat like Skill Knowledge or Aereni Focus.

The other cool trick that this build has is Mercurial Strike plus Robilar's Gambit. Anytime an opponent attacks you and you're unarmed (which should be very achievable, since you have Eldritch Glaive by this point), you can draw a weapon and attack them, and they're flatfooted against the attack, meaning that they take full SA and Iaijutsu Focus damage and have to save against being staggered. Nasty. If you want to lean even harder into this, you could use your spare feats for Dodge and Karmic Strike, letting you do it all again if the opponent actually hits you, and bringing the combo partially online a few levels earlier.

EDIT: Actually, it might be worth keeping Supernatural Transformation (Eldritch Blast) if you're worried about spell resistance; your caster level is best described as "pitiful".

Build (https://forums.giantitp.com/showsinglepost.php?p=24240854&postcount=104)

[Gorthawar]

I'm a fan of warrior skald 1 combined with doomspeak & extra music using your grumbling to debuff the enemy. It also leads nicely into blackguard 3 for an additional -2 on saves and turn undead to power something like death devotion applying negative levels. Even better when you have a swift / free action source for fear like devils aura or intimidating rage / imperious command. Could work for a grumpy old dwarf.

[ShurikVch]

Debuffing feats which are neither fear, nor Sneak Attack-based

Blinded:
Blinding Strike (Dragon #345)

Dazed:
Boomerang Daze (Races of Eberron)
Shield Slam (Complete Warrior)

Deafened:
Deafening Blow (Dragon #345)

Flat-footed:
Surprising Riposte (Drow of the Underdark)

Paralysed:
Freezing The Lifeblood (Complete Warrior)
Paralyzing Fists (Ghostwalk) - Drow of the Underdark version is "newer", but not listed as Fighter Bonus Feat

Sickened:
Brutal Strike (Player's Handbook II)

Slowed:
Staggering Critical (Drow of the Underdark)

Staggered:
Fist of the Heavens (Book of Exalted Deeds) - against Evil creatures

Stunned:
Forceful Staff Style (Ghostwalk) - allow to use Stunning Fist with a staff, and successful stunning allow to initiate a "free" Bull Rush - if no more than 5', it don't count against your number of attacks
Hazing Strike (Secrets of Sarlona) - victims of stunning attacks are unable to regain their altered state of mind (like Rage or Psionic Focus) for 1 round
Staggering Blow (Dragon Compendium) - critical hit with bludgeoning or nonlethal attack
Stunning Fist

Ability Damaged:
Hamstring Attack (Dragon #313) - 1d4 Dex damage (with natural weapon on AoO, or against a flanked/prone/stunned opponent)
Black Panda Mastery II (Dragon #309) - 1 Con damage while using Distant Touch, Freezing the Lifeblood,
Pain Touch, or Stunning Fist feat; it's not a feat, but fighting style - you get the benefit automatically when qualify

Blinded:
Falling Star Strike (Oriental Adventures)
Sand Dancer (Sandstorm)
Sand Spinner (Sandstorm)

Dazed:
Anvil of Thunder (Complete Warrior)
Dire Flail Smash (Champions of Ruin)

Deafened:
Thunderclap (Savage Species)

Fascinated:
Otherworldly Countenance (Fiendish Codex I)

Helpless:
Construct Lock (Races of Eberron)

Knocked Down:
Thunderclap (Savage Species)

Nauseated:
Pain Touch (Complete Warrior)
Three Mountains (Complete Warrior)

Sickened:
Gruesome Finish (Exemplars of Evil)

Stunned:
Disabling Strike (Dragon #339) - against a humanoid Favored Enemy
Pharaoh's Fist (Sandstorm) - ranged AoE stun

Unconscious:
Choke Hold (Oriental Adventures)

Flensing Strike (Eberron Campaign Setting) - -4 on attacks, saves, and checks for a minute

For the "dispelling with a hit" - if you're OK with classes other than Fighter, then Mystic Fire Knight (Champions of Valor) got Spellshatter on 6th level

Also, Spireshard weapon (+3; Dragon #315) - creature damaged with it unable to cast spells or use SLA for 1d4 rounds

[Anthrowhale]

Debuffing feats which are neither fear, nor Sneak Attack-based
That's a nice list. Separating into tiers, you have:

Tier 0: "Dead"
Ability damage to 0

Tier 1: "Half dead" (setup for CdG)
Paralyzed, Unconscious, Helpless

Tier 2: "Deny all or most actions"
Stunned, Dazed, Nauseated, Fascinated

Tier 3: "Deny some actions"
Slowed, Staggered

Tier 4: "Penalties"
Sickened, Ability damage, Blinded, Deafened, Flensing Strike, Flat-footed, Knocked down

Looking through the top 3 tiers, Boomerang Daze still stands out to me since its Fort 10+damage instead of the common Fort 10+level/2+stat. Damage can typically significantly exceed level/2+stat. In addition you can hit twice (via Boomerang Ricochet) and you can make it a touch attack via Master Thrower, and it can work at range.

Pharaoh's Fist also looks notably interesting since it affects all adjacent creatures with stun (Fort DC 10+level/2+Wis). I believe you need to have extra reach to avoid stunning yourself. It looks like Pain Touch adds Nausea for a round. There may be other Stunning Fist riders that are employable.

[King of Nowhere]

I will need to look up stuff in more detail. As it is, I'm realizing a lot of this material requires extra bookkeeping, so I am having some second thoughts. Stunned/dazed works well, because the opponent loses their action without needing to keep track of special penalties, so I may focus on that.

[King of Nowhere]

and/or Shatterspell (https://www.d20pfsrd.com/feats/racial-feats/shatterspell-combat-dwarf/) (dispelling things by hitting them really hard).

wait, I just have to comment on the shatterspell thing.

restricted to one use per day, two at level 15, three at level 20. needs a full standard action to dispel a single effect, when it's normal to have lots of active buffs at high level. and it even stands a fair chance of failing entirely. And if it doesn't fail, most likely it only suppresses the effect for one or two rounds, unless you roll very, very well.
they really were afraid of giving cool stuff to martials, weren't they?

[Kurald Galain]

they really were afraid of giving cool stuff to martials, weren't they?
Not at all; barbarians (who are also martials) can do this at will and multiple times per round, starting from level 6.

[MultitudeMan]

I will need to look up stuff in more detail. As it is, I'm realizing a lot of this material requires extra bookkeeping, so I am having some second thoughts. Stunned/dazed works well, because the opponent loses their action without needing to keep track of special penalties, so I may focus on that.

Your mention of dazing reminded me of Dazed and Confused (https://forums.giantitp.com/showthread.php?609298-Optimization-Showcase-in-the-Playground-Dazed-and-Confused), a fighter-heavy build focusing on Dire Flail Smash which is pretty much online by level 14.